Retrograde Metamorphism in the Greek Cycladic Islands as a Window into Exhumation Mechanisms of High Pressure Terranes

希腊基克拉迪群岛的逆变质作用是了解高压地体折返机制的窗口

• 批准号: 1725110
• 负责人: Jaime Barnes
• 金额: $ 33.48万
• 依托单位: University of Texas at Austin
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2017
• 资助国家: 美国
• 起止时间: 2017-07-01 至 2022-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1725110&HistoricalAwards=false
• 关键词: Retrograde; Metamorphism; Greek; Cycladic; Islands

Subduction zones carry oceanic and continental lithosphere to depths of arc magma genesis and beyond. However, not all subducted material reaches these depths and rocks are often returned to Earth's surface and preserved as exhumed high-pressure and ultra-high-pressure terranes in orogenic belts. The mechanism(s) by which these rocks return to the surface remains enigmatic. Knowledge of exhumation mechanisms is fundamental for a complete understanding of subduction zone dynamics. Although the research focus is on a particular part of the Aegean, the results will have implications for the general tectonic and geochemical processes operative in other exhumed subduction complexes as well as modern and ancient subduction zones. For example, modern observations of subduction zones reveal a spectrum of deformational and seismic behaviors along the subduction interface that are a function of interface effective width, rheological and metamorphic heterogeneities, and fluid distribution. The exhumed rock record on Syros and Tinos samples this subduction interface allowing us to better understand the linkage among mass transport, fluids, deformation and seismic behavior during the return-flow of material. In addition to the intellectual impacts of improved understanding of material transfer in subductions zone, the broader impacts consist of two key components: 1) international collaboration with colleagues at the University of Athens and 2) minority student support/outreach via training of two Ph.D. students (one minority and one female) and support for a minority undergraduate summer internship program for students from the University of Puerto Rico.It is commonly accepted that metamorphic rocks on Syros and Tinos record prograde metamorphism due to subduction during the Eocene (~ 50 Ma), followed by exhumation from mid-crustal levels during Miocene (~25 Ma) extensional detachment faulting. However, the processes responsible for exhuming these rocks from mantle depths to the middle crust during substantial window of time (~25 m.y.) between subduction and core-complex-capture remain enigmatic and the pressure and temperature conditions are poorly constrained. In addition, there are several cryptic phases of retrograde metamorphism that are likely associated with this time gap, and that record different mineral assemblages, deformation fabrics, and degrees of fluid infiltration and fluid sources. THe researchers will determine the pressure-temperature-time-deformation-fluid-source paths for several outcrops on Syros and Tinos, in order to decipher the exhumation mechanisms responsible for the early retrograde history and provide a high resolution snapshot of the Eo-Oligocene exhumation history of the Cycladic Blueschist Unit. The researchers will use a multi-disciplinary suite of approaches, including field structural geology, petrology, geochronology, and geochemistry, to decipher the early exhumation mechanisms of high pressure metamorphic rocks on Syros and Tinos. Field structural geology will focus on establishing deformation stages, strain distributions and kinematics; petrology, thermobarometry and microstructural analysis will be used to link particular fabrics identified in outcrop to their pressure-temperature conditions of deformation; in-situ and multi-mineral-isochron geochronology will provide constraints on the timing of development of particular retrograde fabrics; and stable isotope geochemistry will allow us to decipher the fluid sources that facilitated the retrogression process.

俯冲带载有海洋和大陆岩石圈到弧岩浆起源及其他地区的深度。但是，并非所有俯冲材料都到达这些深度，并且岩石通常被返回地球表面，并保存为造山带中的高压高压和超高压底。这些岩石返回表面的机制仍然神秘。对挖掘机制的了解对于完全了解俯冲带动力学是基本的。尽管研究重点是爱琴海的特定部分，但结果将对其他发掘的俯冲络合物以及现代和古老的俯冲区中的一般构造和地球化学过程产生影响。例如，俯冲带的现代观察结果揭示了沿俯冲界面沿俯冲界面的一系列变形和地震行为，这是界面有效宽度，流变学和变质异质性以及流体分布的函数。在Syros和Tinos样品上发掘的岩石记录这种俯冲界面使我们能够更好地理解材料返回流期间的质量传输，流体，变形和地震行为之间的联系。除了提高对亚折射区域材料转移的理解的智力影响外，更广泛的影响还包括两个关键组成部分：1）通过培训两项博士学位的雅典大学和雅典大学的国际合作和2）少数族裔学生支持/推广。学生（一名少数和一名女性）和支持波多黎各大学的学生的少数本科暑期实习计划，通常接受的是，由于二世（〜50 mA）的衰落，在繁殖期间被散布的次数促成，在繁殖过程中（MAI）造成了25.25次促成，因此在Syros和Tinos创纪录的纪录的纪录的促进性变质上是〜25〜但是，在俯冲和核心复合物捕获之间的实质性时间窗口（约25 m.y）期间，导致从地幔深度到中层地壳中挖出这些岩石的过程仍然存在神秘性，压力和温度条件受到巨大约束。此外，还有几个神秘的逆行变质阶段可能与此时间间隙相关，并且记录了不同的矿物组合，变形织物以及流体浸润和流体源的程度。研究人员将确定几种关于Syros和Tinos的露头的压力 - 温度促进流体源路径，以解释负责早期逆行病史的挖掘机制，并提供EO-Oligeene Sughumation of Cycladic Blueschist单位的高分辨率快照。研究人员将使用多种学科的方法，包括现场结构地质学，岩石学，地球学和地球化学，以破译Syros和Tinos上高压变质岩石的早期挖掘机制。现场结构地质学将着重于建立变形阶段，应变分布和运动学；岩石学，热压法和微结构分析将用于将露头中鉴定出的特定织物与它们的变形条件联系起来。 原位和多矿物异位地质学将对特定逆行织物开发的时机提供限制；稳定的同位素地球化学将使我们能够破译促进倒流过程的流体源。

项目成果

Evaluation and application of the quartz-inclusions-in-epidote mineral barometer

• DOI: 10.2138/am-2020-7379
• 发表时间: 2020-08
• 期刊: American Mineralogist
• 影响因子: 3.1
• 作者: M. Cisneros;K. Ashley;R. Bodnar

Insights from elastic thermobarometry into exhumation of high-pressure metamorphic rocks from Syros, Greece

• DOI: 10.5194/se-12-1335-2021
• 发表时间: 2020-09
• 期刊: Solid Earth
• 影响因子: 3.4
• 作者: Miguel Cisneros;Jaime D. Barnes;W. Behr;A. Kotowski;D. Stockli;K. Soukis

Applications and Limitations of Elastic Thermobarometry: Insights From Elastic Modeling of Inclusion‐Host Pairs and Example Case Studies

• DOI: 10.1029/2020gc009231
• 发表时间: 2020-09
• 期刊: Geochemistry
• 影响因子: 3.7
• 作者: M. Cisneros;K. Befus

Zircon U-Pb and geochemical signatures in high-pressure, low-temperature metamorphic rocks as recorders of subduction zone processes, Sikinos and Ios islands, Greece

• DOI: 10.1016/j.chemgeo.2021.120447
• 发表时间: 2021-11
• 期刊: Chemical Geology
• 影响因子: 3.9
• 作者: Eirini M. Poulaki;D. Stockli;Megan E. Flansburg;M. Gevedon;L. Stockli;J. Barnes;K. Soukis;K. Kitajima;J. Valley

Subduction, Underplating, and Return Flow Recorded in the Cycladic Blueschist Unit Exposed on Syros, Greece

希腊锡罗斯岛上基克拉迪蓝片岩单元记录的俯冲、底侵和回流

• DOI: 10.1029/2020tc006528
• 发表时间: 2022
• 期刊: Tectonics
• 影响因子: 4.2
• 作者: Kotowski, Alissa J.;Cisneros, Miguel;Behr, Whitney M.;Stockli, Daniel F.;Soukis, Konstantinos;Barnes, Jaime D.;Ortega‐Arroyo, Daniel
• 通讯作者: Ortega‐Arroyo, Daniel